def _odd_iter():
	n = 1
	while True:
		n = n + 2
		yield n

def _not_divisible(n):
	return lambda x: x % n > 0

def primes():
	yield 2
	it = _odd_iter() # 初始序列
	while True:
		n = next(it) #返回序列中的第一个数
		yield n
		it = filter(_not_divisible(n), it) #筛选掉这个数的倍数

		
def main():
	for n in primes():
		if n < 1000:
			print(n)
		else:
			break

if __name__ == '__main__':
    main()

